PREHEAT oven to 350°F. Spray 10-cup tube pan or 12-cup fluted tube pan with cooking spray; set aside. Beat eggs, cake mix, sour cream, oil, water and dry pudding mix in large bowl with electric mixer on medium speed 2 min; set aside.
COOK butter and brown sugar in small saucepan on medium-low heat until butter is melted and mixture is well blended, stirring occasionally. Add banana slices; cook 5 min., stirring occasionally. Stir in walnuts; pour into prepared pan. Cover with batter.
BAKE 40 min. or until toothpick inserted near center comes out clean. Cool in pan on wire rack 10 min. Run knife or metal spatula around rim of pan to loosen cake. Invert cake onto rack; gently remove pan. Cool completely.